This works around a hardware bug in "Nimbus" POWER9 DD2.2 processors, where the contents of the TEXASR can get corrupted while a thread is in fake suspend state. The workaround is for the instruction emulation code to use the value saved at the most recent guest exit in real suspend mode. We achieve this by simply not saving the TEXASR into the vcpu struct on an exit in fake suspend state. We also have to take care to set the orig_texasr field only on guest exit in real suspend state. This also means that on guest entry in fake suspend state, TEXASR will be restored to the value it had on the last exit in real suspend state, effectively counteracting any hardware-caused corruption. This works because TEXASR may not be written in suspend state. With this, the guest might see the wrong values in TEXASR if it reads it while in suspend state, but will see the correct value in non-transactional state (e.g. after a treclaim), and treclaim will work correctly. With this workaround, the code will actually run slightly faster, and will operate correctly on systems without the TEXASR bug (since TEXASR may not be written in suspend state, and is only changed by failure recording, which will have already been done before we get into fake suspend state). Therefore these changes are not made subject to a CPU feature bit. Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx> --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 11396c0..736809f 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -3117,10 +3117,6 @@ kvmppc_save_tm: li r3, TM_CAUSE_KVM_RESCHED BEGIN_FTR_SECTION - /* Emulation of the treclaim instruction needs TEXASR before treclaim */ - mfspr r6, SPRN_TEXASR - std r6, VCPU_ORIG_TEXASR(r9) - lbz r0, HSTATE_FAKE_SUSPEND(r13) /* Were we fake suspended? */ cmpwi r0, 0 beq 3f @@ -3130,7 +3126,12 @@ BEGIN_FTR_SECTION_NESTED(96) bl pnv_power9_force_smt4_catch END_FTR_SECTION_NESTED(CPU_FTR_P9_TM_XER_SO_BUG, CPU_FTR_P9_TM_XER_SO_BUG, 96) nop + b 6f 3: + /* Emulation of the treclaim instruction needs TEXASR before treclaim */ + mfspr r6, SPRN_TEXASR + std r6, VCPU_ORIG_TEXASR(r9) +6: END_FTR_SECTION_IFSET(CPU_FTR_P9_TM_HV_ASSIST) /* Clear the MSR RI since r1, r13 are all going to be foobar. */ @@ -3176,7 +3177,8 @@ END_FTR_SECTION_NESTED(CPU_FTR_P9_TM_XER_SO_BUG, CPU_FTR_P9_TM_XER_SO_BUG, 96) andc r3, r3, r0 mtspr SPRN_PSSCR, r3 ld r9, HSTATE_KVM_VCPU(r13) - b 1f + /* Don't save TEXASR, use value from last exit in real suspend state */ + b 11f 2: END_FTR_SECTION_IFSET(CPU_FTR_P9_TM_HV_ASSIST) @@ -3250,12 +3252,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_P9_TM_HV_ASSIST) * change these outside of a transaction, so they must always be * context switched. */ + mfspr r7, SPRN_TEXASR + std r7, VCPU_TEXASR(r9) +11: mfspr r5, SPRN_TFHAR mfspr r6, SPRN_TFIAR - mfspr r7, SPRN_TEXASR std r5, VCPU_TFHAR(r9) std r6, VCPU_TFIAR(r9) - std r7, VCPU_TEXASR(r9) addi r1, r1, PPC_MIN_STKFRM ld r0, PPC_LR_STKOFF(r1) -- 2.7.4
